Breakup of asymmetric liquid ligaments

The evolution of a finite liquid ligament into either a single drop or several droplets is driven by the competition of two simultaneous processes: The recoil and the pinch-off. Scalings providing the kinetics of each process can be compared to predict the breakup of cylindrical symmetric ligaments. Here, asymmetric ligaments formed by a main drop connected to a cylindrical tail and commonly produced by inkjet printing are considered. Using two print heads, 16 inks, and various printing parameters, we show the limits of commonly admitted scalings for asymmetric ligaments. The recoil is governed by a modified Taylor-Culick velocity and a complex drainage, possibly leading to pinch-off, develops at the junction of the ligament with the main drop. The ligament aspect ratio affects this process for which two regimes must be accounted for. Finally, the ratio between the recoil and pinch-off timescales successfully predicts asymmetric ligament breakup.